Source: San Jose Mercury News, March 3, 2011
Posted on: http://enr.construction.com
By: Steve Johnson
A PG&E inspector has expressed concerns to federal investigators about the methods used in 2008 to install a sewer line just inches below the natural gas line that erupted in San Bruno on Sept. 9, according to documents made public this week.
The sewer project under investigation by the National Transportation Safety Board is of concern to some experts and government regulators in large part because the work involved a procedure that produces violent ground shaking. The inspector said the sewer line was installed without his direct oversight and closer to the gas pipe than he wanted — a claim the contractor on the job disputes in part. But the inspector ultimately concluded that the work “seemed to be OK.”
Although it’s unclear if the construction played a role in the San Bruno explosion, which killed eight people and destroyed 38 homes, it’s possible it could have weakened the shoddy welds that have recently been found to be riddling the ruptured gas line, according to Richard Kuprewicz, a Washington state pipeline safety expert. He added that the disclosures raise questions about how diligently PG&E was monitoring the sewer work.
“It clearly is a symptom of some other problems,” he said.
The California Public Utilities Commission, which is conducting its own probe of the San Bruno accident and PG&E’s overall pipeline operations, also intends to look into the sewer job, said Richard Clark, the agency’s consumer
product and safety division director.
“We’re very interested in further investigating this matter,” he said. “We’re interested in what PG&E knew, and whether action by the Contractors State License Board is appropriate against the contractor, if the facts warrant.”
PG&E spokeswoman Katie Romans declined to comment, and the sewer contractor, D’Arcy and Harty Construction of San Francisco, could not be reached for comment.
In May 2008, San Bruno approved a contract with D’Arcy to replace 1,670 feet of aging sewer pipes, which crossed under the doomed gas pipeline at Earl Avenue and Glenview Drive.
The contractor used a method called “pipe bursting,” in which its crews pulled a large, cone-shaped device through the aging sewer pipe, shattering the line and pulling a new pipe in behind it. While the technique avoids digging trenches in the street and inconveniencing residents, it can cause ground shaking and disruption of adjacent soil and rock.
Although the sewer work near the pipe was first reported by the Mercury News three days after the Sept. 9, 2010, explosion, the safety board’s interviews reveal the dispute between PG&E and the sewer contractor over the construction.
Steven Poulo, the PG&E inspector monitoring the sewer project, told investigators he had instructed D’Arcy to let him know when the sewer would be installed under the gas pipe. But he said that didn’t happen, and the next time he went out there, he discovered the work already had been done.
Enough of the pipes were still exposed that he said he could tell with a tape measure that the two lines were about 10 inches apart, which was less than the one-foot separation he had wanted. While Poulo had written on a form reviewed by investigators that the clearance was only six inches, when interviewed he said he thought 10 inches was more accurate. Although Poulo said he considered the clearance between the pipes sufficient, “I wasn’t satisfied” that the sewer was installed under the gas main in his absence. He also complained that the contractor filled the area around the gas line with gravel, rather than sand, which PG&E requires.
But John Harty, D’Arcy’s co-owner, disputed Poulo’s contention, saying “he was there,” according to the newly released documents.
Jose Ornelas, a D’Arcy foreman who oversaw the sewer project, also said Poulo was at the construction site when the work was under way near the gas line, but that Poulo left before it was completed that day.
After the sewer line’s installation under the gas pipe, Ornelas said, he called Poulo to drop by to look at the job. When Poulo saw how close the lines were, he made several phone calls to determine what to do about it and came up with a solution, Ornelas said.
“He say, ‘OK, just put something between them,’ ” Ornelas said in his interview with investigators. “So I told him, ‘What am I going to put?’ He said, ‘I don’t know, put a piece of wood.’ ”
Noting that he has overseen many sewer line installations near PG&E gas lines, Ornelas said that was the first time he’d ever placed wood between the pipes.
When Poulo was interviewed by the safety board, however, he denied ordering the use of the wood, saying “that would not be allowed.”